1. Field of the Invention
The present invention relates to a data transmission apparatus and a method thereof for sending and receiving data recorded on a recording medium such as an optical disk, magnetic tape and the like, to and from an external equipment via a digital interface such as IEEE 1394 Standard, using a command adapted thereto.
2. Description of the Prior Art
Recently, usage of IEEE 1394 Standard has been increased in a serial data transmission system. The IEEE 1394 system can be used not only for transmission of computer data which is conventionally conducted by a SCSI system or the like, but also used for transmission of substantive audio and/or video (referred to as xe2x80x9cAVxe2x80x9d, hereinafter) data to be processed by an AV equipment. This is because the IEEE 1394 system has two communication methods defined therein, i.e., an isochronous data transmission system and an asynchronous data transmission system.
The isochronous communication is a data transmission method which can be used for transmitting data, such as substantive AV data, requiring a real time property. In this method, a frequency band required for the data transmission is previously obtained prior to the start of the data transmission, and then the data transmission is conducted using the band. By this arrangement, the real time property of the data transmission can be assured.
Meanwhile, the asynchronous communication is a data transmission method using a free time for transmitting auxiliary data such as command or computer data and the like data which does not require a real time property. This communication method can be regarded as equivalent to a conventional SCSI method.
Various standards are proposed as a host transmission protocol on the IEEE 1394 system, and IPC 61883 standard is used as one of the methods. The IEC 61883 standard specifies such as a method of sending and receiving AV data requiring real time property in an isochronous communication system, and also specifies a method of sending and receiving a command to be given to an AV equipment in an asynchronous communication system.
A set of AVIC commands and responses are transported by Function Control Protocol (FCP) defined by IEC 61883. FCP provides a simple means to encapsulate commands and responses within IEEE 1394. The scope of the present invention field is within the AV/C commands and responses defined by IEC 61883. The format of an FCP frame encapsulated within a Serial Bus block packet is shown in FIG. 8.
As shown in FIG. 8, the format of FCP frame is encapsulated within a Serial Bus packet where one rank i.e. one quadrate corresponds to 32 bits and the first five ranks (i.e., first five quadrates) are used as a header of a packet in the asynchronous system on IEEE 1394 Standard, and the following xe2x80x9cctsxe2x80x9d and FCP data fields are subsequently transmitted. In this format, destination ID, source ID, and the like fields are defined where the cts field defines the command transaction format used by the FCP frame. Commands originated by a device at a serial bus node (i.e., a controller) are addressed to the FCP COMMAND register (i.e., destination_offset) at the serial bus node that contains the device to be controlled (i.e., the target). The data payload of both FCP request and response packets, specified by data_length, is limited to a maximum of 512 bytes.
FIG. 9 shows a structure of an AV/C command frame which is up to 512 bytes of command payload. The AV/C commands and responses are encapsulated within FCP frames and are transmitted between the controller and target FCP_COMMAND and FCP_RESPONSE registers. In this command frame structure, a xe2x80x9cctypexe2x80x9d l field is defined for indicating a command type as to whether the command is a control one or an inquiring one. The subunit_type and subunit_ID fields are defined for identifying a type of an AV equipment and the subsequent opcode and operands [0] to [n] indicate an actual command such as PLAY, STOP, RECORD and the like. All of the operands are optional and defined by ctype, subunit_type and opcode.
In the case where a compact disk or mini disk is used as a data recording medium in a disk drive unit for recording and reproducing substantive data such as, for example, audio (and/or video) data, the disk is also provided with auxiliary attributive information as well as the substantive audio (and/or video) data recorded thereon.
As shown in FIG. 10, the attributive information is recorded in a TOC (Table-Of-Contents) region of a compact disk or in a UTOC region of a mini disk.
In the case of audio data such as music recorded in a disk, the attributive information includes a start address and end address of the music data, title of music, recorded date/time of the music data and the like information. There is no defined method of transmitting such attributive information in the serial data transmission on the EEC 61883 standard. Therefore, in the conventional data transmission system, there are proposed a method of storing the attributive information in a data format of a list structure and a method of accessing the listed attributive information from an external equipment.
FIG. 11 shows an example of the conventional data transmission system of storing and accessing the listed attributive information. In this example, a data transmission apparatus 1000 having, e.g., an optical disk 1004 loaded therein is electrically connected to an external equipment 1001 via a digital interface 1002, where the optical disk 1004 is provided with substantive AV data and attributive information data of the AV data recorded thereon. The attributive data includes data number of the AV data (which indicates the number of musics when the AV data is music audio data), total reproduction time, reproduction time of individual AV data, title of the disk, titles of AV data, and the like.
When the optical disk 1004 is loaded on the apparatus 1000, the attributive information such as data number of the AV data, total reproduction time, reproduction time of each AV data, each title and the like data are reproduced and stored as an attributive information list illustrated as a first list 1003 in a register storage portion of the apparatus.
Meanwhile, status information indicating the present operation status of the apparatus 1000 such as reproduction or stop and the like, present reproduction position, present reproduction method such as normal reproduction or program reproduction and the like, are stored as a status information list illustrated as a second list 1005 in the register storage portion of the apparatus.
FIG. 12 shows a conventional example of a concrete data pattern format construction of the attributive information list 1003 having a structure of three class layers. In the first layer structure, a packet header is positioned at the top and the attributive information groups of the AV data (illustrated as first, second, third musics . . . ) are arranged below in turn. In the second layer structure, the packet header is comprised of header length indicating a specified byte length of the header and the entire attributive information contained in the disk while the attributive information group of each AV data is comprised of a data header including a data length and attributive information contents of each AV data.
As shown in the third layer structure, the entire disk attributive information is comprised of information blocks including an entire reproduction time, title of the disk, number of musics and the like, each having a specified byte length of e.g. four bytes while the attributive information contents of each AV data includes a reproduction time, title and the like of each AV data, each content having a data length of a specified bytes number.
On paying attention to the third stair layer structure of the data pattern format shown in FIG. 12, when an attributive information content such as, for example, a specific title of music, is desired to be accessed, the accessing must be conducted by designating the address position in bytes from the top position in the list. However, because the data pattern of the attributive information list is of a variable length format, the address position in bytes of the desired attributive information content is not always constant in the list.
In the construction shown in FIG. 11, when a user desires to input an attributive content, e.g. a title of disk into the optical disk 1004 in the apparatus 1000, the desired title is written onto the position of the title of disk in the attributive list 1003 in accordance with a command sent from the external equipment 1001 via the digital interface 1002. When the optical disk 1004 is ejected to the apparatus, the attributive information written into the desired region of the list 1003 is recorded in the corresponding region of the optical disk 1004. When the optical disk 1004 is loaded on an apparatus, a new attributive information list 1003 is produced in the apparatus based on the attributive information recorded on the optical disk 1004. When the attributive information such as reproduction time and title data recorded in the optical disk 1004 is desired to be obtained by the external equipment, the desired attributive information can be obtained by the external equipment 1001 via the digital interface 1002 by accessing the corresponding region in the first list 1003 within the apparatus 1000.
When the user desires to obtain the present operation status information of the apparatus 1000, the desired status information of the apparatus can be obtained by accessing to the status information list (i.e., illustrated as the second list 1005). For example, by reading out the present operation status information from the second list 1005, the user obtains the information as to in what status the apparatus is under operation at present, via the interface and via the external equipment 1001.
In the conventional system, however, since the contents of the attributive information and the arrangement order thereof in the first list 1003 are fixed, therefore when a new recording medium having new attributive information recorded therein is used in the apparatus in the future, a new attributive information list must be defined as exclusively dedicated for the medium.
Moreover, in the conventional method as described above, when accessing the attributive information contained in the first list 1003 for reading or writing, the accessing position in bytes must be designated from the top position in the list. Therefore, in the case where the attributive information is written into the first list 1003 for overwrite or insertion thereof by way of the external equipment, if an input of the information content is erroneously performed even in one byte position in the list, the resultant content is undesirably different from the exact content to be written. In this undesirable case of erroneous byte position, it is difficult for the external equipment to confirm the erroneous byte position in writing the desired information in the first list 1003 because the external equipment confirms the information list read out from the apparatus 1000 as a series of bytes sequence.
Furthermore, a byte position of a desired attributive information content in the list is varied every time the list is renewed. Therefore, when in accessing for writing attributive information, the present list of the attributive information must be first read to confirm the byte position of the desired attributive information content in the list prior to conducting the writing operation, which necessarily increases the processing amount of the operation. The conventional method has problems as described above.
The present invention has been developed to solve these problems inherent to the conventional data transmission apparatus, and an essential object of the present invention is to provide an improvement of a data transmission apparatus and method thereof using a specific command adapted thereto, which is capable of easily varying contents and arrangement order of auxiliary information contents in a list, and also capable of writing and reading the auxiliary information into and from a precise position when accessing thereto, whereby even when a list of the auxiliary information is renewed, it is not necessary to identify a byte position of the information in the list, and therefore a desired auxiliary information can be easily accessed by way of the same designation method, and whereby a user can obtain a list of attributive information contained in the recording medium or a list of status information of the apparatus by a simple construction and method.
In order to achieve the objects mentioned above, the present invention provides a data transmission apparatus for sending and receiving main data recorded on a recording medium to and from an external equipment via a digital interface based on command data sent from the external equipment, which the apparatus comprises:
an auxiliary information storage means for storing auxiliary information relating to a transaction of the main data; and
a list producing means for producing a list of the auxiliary information by appending a corresponding ID code to each content of the auxiliary information group, based on a table of the ID codes previously assigned to the contents of the auxiliary information, to thereby access a desired auxiliary information content in the list with reference to the ID code appended thereto.
In this construction, the entire list of the auxiliary information includes a plurality of auxiliary information groups, each group having a data format construction including continuous plural pairs of auxiliary information contents and corresponding ID codes added thereto.
Another object of the present invention is to provide a data transmission method for sending and receiving main data recorded on a recording medium to and from an external equipment via a digital interface based on command data sent from the external equipment, which the method comprises the steps of:
storing auxiliary information relating to a transaction of the main data;
producing a list of the auxiliary information by appending a corresponding ID code to each content of the auxiliary information group, based on a table of the ID codes previously assigned to the contents of the auxiliary information; and
accessing a desired auxiliary information content in the list with reference to the ID code appended thereto.
Further another object of the present invention is to provide command data adapted to the apparatus, wherein the command data, which is a command for accessing an auxiliary information content, includes an ID-code field indicating an ID code of the desired auxiliary information content to be accessed, whereby the desired auxiliary information content is identified in address position in the list and obtained by accessing.
By this arrangement, in the data transmission apparatus and method thereof according to the present invention, when the data recorded in the recording medium is transmitted between the apparatus and the external equipment, a list structure of the auxiliary information of transaction of the main data is used, which the list is produced by appending a corresponding ID code to each of the auxiliary information contents, the ID codes previously assigned to the contents of the auxiliary information group. When accessing the contents in the list, the ID codes are used as an accessing key for obtaining the desired auxiliary information. Therefore, even when an auxiliary information group is increased, the contents of the increased auxiliary information group can be easily accessed merely by defining the ID codes corresponding to the newly added contents while maintaining the essential structure of the list pattern format. Also, it is not necessary to fix the arrangement order in writing of the auxiliary information and the order in the list can be optionally modified.
Moreover, since the ID codes are used as the accessing key for the auxiliary information, it is not necessary to designate the address position in bytes from the top in the list as required in the conventional method, and therefore accessing an erroneous position in the list can be effectively avoided, which assures the precise access to the desired auxiliary information. Moreover, since the access to the auxiliary information is performed using ID codes as a searching key, it can be omitted to first read the list and identify the position in bytes of the desired information when in writing operation as required in the conventional method, and thus the processing amount of the data can be remarkably reduced.
In addition, in the data transmission apparatus of the present invention, when the auxiliary information such as attributive information recorded in the recording medium or status information of the operation condition of the apparatus is stored in a list structure, the list is produced by adding corresponding ID codes to actual auxiliary information contents. And the accessing to the auxiliary information list is performed using the ID codes as the accessing key, and therefore the reading and writing of the auxiliary information can be easily conducted.
Furthermore, when command data is transmitted from the external equipment to the apparatus for inquiring what kinds of auxiliary information contents are stored in the apparatus, the apparatus produces a list of the ID codes of the attributive and status information stored in the apparatus and then the produced list of the ID codes are transmitted to the external equipment as a response to the command. The inquiring operation can be performed with regard to not only the entire of the attributive and status information but also a part thereof, and the list of the ID codes of the desired attributive and status information is made in accordance with the range of the inquiring contents of the command.
As described above, even when a user desires to obtain as to whether or not the data transmission apparatus holds optional auxiliary information contents it is not necessary to directly read out all of the desired information contents. Accordingly, the auxiliary information list held in the apparatus can be easily obtained by way of the external equipment. Thus, the data processing amount of the apparatus and the external equipment can be reduced together with reduction of the traffic amount on the digital interface.